One mode by which vehicles may emit pollutants is during inactive periods in which fuel is vaporized and released from the vehicle into the atmosphere. The allowable levels of evaporative emissions is continually being decreased. As a consequence, vehicle manufacturers have developed and installed systems for managing fuel vapors emanating from fuel tanks. Also, measures are taken to reduce the amount of unburned fuel residing in the engine which could be released into the atmosphere during periods during which the vehicle is not operating.
The inventors of the present invention have recognized that engines equipped with electronically deactivatable valves present an opportunity for managing unburned fuel during an engine shutdown procedure not possible with conventional engines which have no provision for disabling the valves.